Engine derate in 3 hrs, seek service immediately!

I’m just local dirt hauler, and this whole DPF system is new to me. So I was told to not keep topping up def fluid. Let the older stuff run down then put a few gallons in. I only did this once but won’t run it down to red level again

 

Here’s an update. the mechanic pinned it out and found the return from sensor losing volts. So he ran an overlay from the pin directly to the sensor. Drove home. Thought was all done. Then exact same again next day on first load. We’re all at a loss here. Gonna now try overlay the supply to see if this fixes. If not I’m gonna have to cut losses and bring it to KW dealer. Downtime plus what I paid mechanic starting to add up now.

 

Just wanted to update. Ended up bringing truck to Kenworth. Figured out harness issue (which we knew). And found that the supply from pin to sensor was problem. Found out that part of harness was $2k plus $3500 labor. They gave me choice to do another overlay same as my mechanic did instead of full harness at cost of $1500 so I went with that. Got truck back and worked 2 weeks hard with no check engine light. So relieved. Glad to be back up and running. Thanks to everyone who replied and helped on this post.

 

Had same problem. It happens to me when is fog present. Just go on dry weather, sun preferably, open your hood and wait 1 hours minimum with engine off. It works for me every time it happens.